Security researchers recently discovered a vulnerability in the Mozilla Firefox web browser and Thunderbird email client software that could allow attackers to modify an add-on's underlying file without being detected. The vulnerability is assigned identifier CVE-2022-26387, and it affects Firefox versions below 98, Firefox ESR versions below 91.7, and Thunderbird versions below 91.7.

In this post, we will take a closer look at the details of this vulnerability, explore the potential risks associated with exploiting it, and discuss the available patches and mitigation strategies. We will also provide code snippets to help understand the technical aspects of the vulnerability.

The Vulnerability

When a user tries to install an add-on in Firefox or Thunderbird, the application checks for the add-on's digital signature to ensure that it is a genuine and trustworthy source. However, in affected versions of the software, while add-on signature verification occurs before the user is prompted, the add-on file can be modified without being noticed after the signature verification but before the user confirms the prompt.

This means that an attacker could exploit this vulnerability to inject malicious code into the add-on, potentially leading to the compromise of the user's system or data. The attack can happen if the user installs the extension from a compromised source or if their local system is compromised in the case of an offline installation.

Code Snippet

The code snippet below demonstrates a simple example of how the add-on signature verification bypass could be exploited. Note that this is for educational purposes only and should not be used for malicious activities.

// Original add-on code
function install_addon() {
	validate_signature();
	prompt_user();
	install();
}

// Exploit: Inject malicious code after signature validation but before user prompt confirmation
function exploit_addon() {
	try {
		validate_signature();
	} catch {
		return false;
	}

	// Malicious code injection
	inject_malicious_code();

	prompt_user();
	install();
}

Original References

The vulnerability was first reported by the security researchers who discovered it. You can find more details about the vulnerability and exploitation methods in their original report:

- Mozilla Security Advisory: CVE-2022-26387
- Mozilla security blog post discussing the vulnerability

Exploit Details

As mentioned earlier, exploiting this vulnerability requires either a compromised source or a compromised local system, and successful exploitation could lead to the complete compromise of the user's information or their machine.

This vulnerability is categorized as a race condition, which means it depends on the exact timing of events to succeed. Therefore, exploiting it may not be trivial and might require experimentation and manipulation of variables such as system load or other processes.

Patches and Mitigation

To fix this vulnerability, Mozilla has released updated versions of Firefox, Firefox ESR, and Thunderbird. Users should immediately update their software to the latest version:

- Firefox 98
- Firefox ESR 91.7
- Thunderbird 91.7

Additionally, users should always be cautious when installing add-ons, especially from untrusted or unknown sources. They should also maintain up-to-date system security and learn about best practices for protecting their data and devices.

Conclusion

CVE-2022-26387 is a potentially high-risk vulnerability in the Firefox web browser and Thunderbird email client software. While the exploitation of the vulnerability may not be straightforward, the potential impact of successful exploitation makes it critical for users to update their software to the latest version and exercise caution when installing add-ons.

For more information about this vulnerability and threat mitigation strategies, please refer to the resources mentioned in the original references section of this article. Stay secure and be vigilant.

Timeline

Published on: 12/22/2022 20:15:00 UTC
Last modified on: 12/30/2022 16:04:00 UTC